1. Field of the Invention
The present invention is related to providing a signal receiving control system of a remote control, and particularly, to providing a control device which receives a signal only for the duration of each of the sampling pulses, and a control method thereof.
2. Description of the Prior Art
A conventional remote control includes a receiving unit which decodes a control signal sent by a transmitting unit as illustrated in FIG. 1. The receiving unit counts the time intervals between two successive falling edges of given pulse signals and discriminates signals "0" and "1" indicative of a data code to determine the presence of a desired or correct signal. The control signal generally contains a reader pulse and a combination of data pulses, each of which has a predetermined time interval corresponding to a binary number, "0" or "1". The time intervals 2t and t between successive falling edges are converted into data codes "1" and "0" of a binary signal respectively, so as to control, for example, the operation of an appliance. The data code represented in FIG. 1 expresses "1001" after the reader pulse.
However, a remote control uses a carrier with a frequency band of 30 to 40 KHz, while the power frequency of a common commercial electronic fluorescent lamp device extends from 20 to 40 KHz. This causes problems in decoding the received control signals and leads to the malfunctioning of the appliance. This results because the control signals from the transmitting unit are similar in waveform to the noise signals concurrently being received from the electronic fluorescent lamp device. In other words, the microprocessor of the receiving unit interprets the noise signals as normal control signals. Thus, the desired appliance operation is impaired or prevented. Furthermore, the appliance is not operated due to the environmental condition that the custom code thereof are different from codes set by the input signals.
In order to resolve these problems, Japanese Laid-Open Patent No. 284533/1990 discloses an infrared remote control which comprises means arranged in a transmitting unit for generating the carrier frequencies of N channels and means arranged in a transmitting unit for selecting one of the carrier frequencies of N channels. Also, at least one narrow band pass filter is arranged in the receiving unit for filtering the frequency corresponding to the carrier frequency of N channels. Switching means are arranged in the receiving unit for changing the carrier frequency into a narrow band frequency in which the transmitting unit generates the carrier frequencies of N channels. The receiving unit receives the carrier frequency signal passing through the narrow band pass filter corresponding to the channel switching selection. However, this device increases production costs and increases complexity because additional carrier generating units, carrier selecting elements, narrow band pass filters and switching elements are required in order to guarantee product reliability.